1. Technical Field
The present invention relates to an amplifier unit and a mobile electronic device provided with the amplifier unit.
2. Related Art
Recently, multifunctional mobile electronic devices such as mobile phones, tablet terminals, and PDAs have become widely popular. Such mobile electronic devices may be used for the purpose of recording sound or recording video. However, because most mobile electronic devices are not dedicated to recording sound (or recording video), a microphone suitable for recording sound is not mounted in many cases. With this being the situation, stereophonic microphone devices attachable as desired to such mobile electronic devices have been proposed.
On the other hand, various types of microphone devices or stereophonic input and output devices are known, although they are not stereophonic microphone devices specifically attachable to mobile electronic devices.
JP 07-288162 A discloses a stereophonic input and output device having an L channel input terminal and an R channel input terminal arranged on the same surface, wherein, when both of the input terminals are in connection, a signal is input and output as a stereophonic balanced signal, and when only one of the input terminals is in connection, a signal is input and output as a stereophonic unbalanced signal.
JP 2006-033615 A discloses a sound pickup device capable of changing the orientation of a microphone in accordance with the purpose of use, and discloses switching between stereophonic sound recording and monophonic sound recording in accordance with the position of the microphone relative to the main body of the sound pickup device.
In order to increase the sound quality of a stereophonic microphone device attached to a mobile electronic device, an amplifier unit comprising an analog-to-digital converter, an input volume control capable of adjusting an input level, and other components, to which an external stereophonic device can be connected as desired, is contemplated. In consideration of the fact that such an amplifier unit is attached to a mobile electronic device, flexibility is desired such that the amplifier unit can support diverse sound recording scenarios.